This invention relates to a digital image demodulating apparatus for outputting a digital image signal inputted to a main body to a display device such as a monitor, and particularly to a digital image demodulating apparatus for converting and outputting a digital image signal corresponding to an aspect ratio of a display device when an aspect ratio of a digital image signal inputted differs from an aspect ratio of a display image of a display device outputted.
In a screen of a display device such as a monitor or a liquid crystal display, there are plural standards in an aspect ratio which is a dimension ratio of height to width, and an image signal of DVD, video, television broadcast, etc. includes an image signal having plural specifications corresponding to these aspect ratios. For example, there are things of an aspect ratio of 4 to 3 or an aspect ratio of 16 to 9 with a wider size than this.
As a result of this, plural apparatus and methods for display with the minimum strange feeling when an aspect ratio of the image signal differs from an aspect ratio of a display screen are proposed.
Particularly, a method shown in FIGS. 4A and 4B is devised as a method for displaying an image signal with an aspect ratio of 4 to 3 on a display screen with an aspect ratio of 16 to 9.
FIGS. 4A and 4B are schematic diagrams showing a state of displaying an image signal with an aspect ratio of 4 to 3 at an aspect ratio of 16 to 9, and FIG. 4A is a diagram showing a lateral uniform expansion method and FIG. 4B is a diagram showing a side panel method.
The lateral uniform expansion method shown in FIG. 4A is a method for expanding an image frame 1 with an aspect ratio of 4 to 3 horizontally uniformly and converting the image frame into an image frame 5 with an aspect ratio of 16 to 9, but the entire presence image part 2 expands laterally, so that an image 11 displayed on a screen is deformed from an image 10 and, for example, a perfect circle of the image 10 becomes a horizontally long ellipse of the image 10 to be displayed. On the other hand, the method shown in FIG. 4B is a method for placing side panels 4 of a non-signal part in both ends of a horizontal direction of the image frame 1 with the aspect ratio of 4 to 3 and forming the image frame 5 with the aspect ratio of 16 to 9. A display screen is formed of the presence image part 2 with the substantially same shape as that of the original image and the side panels 4.
Thus, in the lateral uniform expansion method, the image is displayed on the entire screen of a display device, but the displayed image expands laterally, so that the original image shape cannot be maintained. On the other hand, in the side panel method, the image cannot be obtained on the entire screen but the original image shape can be reproduced and displayed faithfully.
Further, a digital image demodulating apparatus comprising converter according to a relation between an aspect ratio of such an original image signal and an aspect ratio of a display device is disclosed in a publication of the Unexamined Japanese Patent Application Publication No. Hei9-326974. According to this publication, image display without a strange feeling is performed by making conversion of the image signal automatically according to the aspect ratio of the original image signal and the aspect ratio of the display device. Here, an image signal with an aspect ratio of 4 to 3 is moved to the center of an area of an aspect ratio of 16 to 9 and is expanded laterally or side panels are added to both lateral ends and the image signal is converted into an image with the aspect ratio of 16 to 9.
Further, a display apparatus for displaying another image with an aspect ratio of 4 to 3 on a display screen with an aspect ratio of 16 to 9 is disclosed in a publication of the Unexamined Japanese Patent Application Publication No. Hei10-150614. According to this publication, when a display device with specifications of the aspect ratio of 16 to 9 receives an image signal with the aspect ratio of 4 to 3, non-signal parts are added to both lateral ends of the image signal and an image without a strange feeling is displayed.
In such a method of conversion and display of the image of the case that the aspect ratios differ, there was the following object to be solved.
In the conventional art described above, a display method to the display device with the aspect ratio different from that of the image signal is provided and switching of display is performed automatically by setting etc. of a user.
However, in some conventional display devices with an aspect ratio of 16 to 9, conversion is made automatically by the lateral uniform expansion method when an image signal with an aspect ratio of 4 to 3 is inputted. In this case, the original image size cannot be maintained and lateral expansion of the image occurs always and a difficult-to-view is caused.
Further, the art disclosed in the Unexamined Japanese Patent Application Publication No. Hei9-326974 must preset whether to perform lateral uniform expansion or add side panels when an image with an aspect ratio of 4 to 3 is displayed in a display device with an aspect ratio of 16 to 9. Here, in the case of being set to a lateral uniform expansion mode, an output is produced to the display device without performing image processing with respect to the image with the aspect ratio of 4 to 3 inside a digital image demodulating apparatus and the display device expands an image signal laterally uniformly. In this case, the image with the aspect ratio of 4 to 3 is directly expanded to an image with an aspect ratio of 16 to 9, so that lateral expansion of the image occurs. Further, in the case of being set to a side panel addition method, by the digital image demodulating apparatus, side panels are previously added to the image with the aspect ratio of 4 to 3 and conversion is made into an image with an aspect ratio of 16 to 9 and then an output is produced to a display device, so that the display device displays the image without performing image processing.
Further, in the Unexamined Japanese Patent Application Publication No. Hei10-150614, the art about the display device (display apparatus) is merely shown and a problem of automatic lateral uniform expansion resulting from the difference between the original image signal and the display device in the aspect ratio as described above is not considered.